1. Field of the Invention
In general, the present invention relates to systems and methods that monitor the functionality of electric elements, such as incandescent bulbs and light emitting diodes. More particularly, the present invention relates to systems and methods that are capable of monitoring the failure of an electrical element even if that electrical element were to fail when powered off.
2. Prior Art Description
Many machines, such as automobiles, appliances, industrial equipment, and the like include small electrical elements such as lights. Some of the lights, especially the lights used to illuminate control panels, are important in the proper and safe operation of the machine. Take, for example, an automobile. The automobile has many obvious lights such as the headlights and brake lights. However, the automobile also has numerous safety system lights that the vehicle owner may never see. The safety system lights include the check engine light, the low oil light, and numerous other safety system lights that indicate that some system of the automobile is in danger of failing. Should one of the safety system lights fail, the driver of the automobile may have no indication that some system has failed. This may result in catastrophic failure. For example, if the low oil light in an automobile fails and the automobile has an oil leak, the driver may be unaware of the condition until the engine seizes for lack of oil. Likewise, consider a light failure in an airplane that prevents a pilot from detecting a potential engine stopping condition.
In the prior art, there are many circuits that have been designed to indicate to a person that a specific electric element has failed. Many of these circuits use complex transistor configurations to monitor the flow of current through a light. Accordingly, the cost of such monitoring circuits is significant and the economics limits the use of such circuits. Such complex prior art circuits are exemplified by U.S. Pat. No. 4,348,613 to Hormel, entitled, Lamp Failure Indicator Circuit.
Other complex prior art circuits optically detect whether or not a lamp emits any light when activated. Such prior art circuits are exemplified by U.S. Pat. No. 6,963,170 to Higgins, entitled Lamp Monitor And Lamp. These light detector circuits also have significant costs that limit their application.
A problem associated with both types of prior art monitoring systems is that a broken electrical element, such as a safety light, cannot be detected until that light is powered on and fails to light. In many machines, electrical elements, such as lights, fail when the electrical element is powered off. Failure of a light may be due to corrosion, vibrational fatigue, water damage, or even terrorist sabotage. If such a failure occurs, the operator of the machinery has no warning of the failure until it is too late. For example, suppose the reverse lights on a tractor-trailer fail due to vibrational damage while the truck is in transit. The driver of the truck would have no way of knowing that the lights have failed until the driver puts the truck into reverse. At that point, the driver may be committed to backing the truck in reverse and now has to do so with no light.
A need therefore exists for a simple, low cost circuit that can warn a person about the failure of an electrical element at the moment of the failure, regardless of whether the electrical element is powered on or off. This need is met by the present invention as described and claimed below.